The specification of European Pat. No. 0 000 437 discloses a collapsible support, in the form of a lie-back push chair, comprising a rear frame having two upper corners and two lower corners; a base frame having two front corners and two rear corners pivotally connected, respectively, to the two lower corners of the rear frame; two upper brace members respectively pivoted, at their upper ends, to the upper corners of the rear frame; two lower brace members respectively pivoted, at their lower ends, to the front corners of the rear frame; two knuckle joints respectively connecting the two upper brace members to the lower brace members so as to prevent folding of the rear frame towards the base frame when the support is extended with the upper brace members respectively extending substantially colinearly with the lower brace members, but to allow the knuckle joints to move, respectively, towards the rear corners of the base frame; two seat support members having rear ends pivotally connected, respectively, at or adjacent the rear corners of the base frame and having front ends respectively supported by the two lower brace members; and two backrest members having lower ends respectively pivoted to the seat support members.